I'm really pleased with the install, and we are making 40 to 50kWh a day at the moment. So now for some paperwork...
One bit is a micro generation certificate, this confirms it is all installed by approved installers, etc, and has the details. I need that for and export tariff.
I have been discussing with the installers - we have a 12.09kW system (i.e. 31 x 390W panels), but they are east / west split so never all get direct sunlight. With the split and roof angle they have determined that maximum is going to be around 9kW, so a 10kW inverter is more than adequate. It will be interesting to see in the height of summer - but interestingly, even though only April, the generation in June won't necessarily be as good as you expect just by sun angle, because it is hotter. Being hotter makes the panels less efficient, so may cancel out the extra sun angle.
I heard there is some trick with some panels with water cooling, i.e. using the waste heat as a heat pump and keeping the panels cool for maximum PV. But we don't have that :-)
So, I may be making 9kW some days, yay. But what do I do with that?
As you will have read, the primary target for this my own usage, and then the excess power goes to a battery, so I can then use the power later when the sun is not shining as much - maybe covering my whole 24 hour day's usage for most if the summer, which is mental.
The bad news!
The battery is likely to be August. So 4 months of no battery. So, I'll export to the power grid, simples!
Well, yes, but that needs paperwork to. The Distribution Network Operator have to give permission to connect, which they have. The DNO decide what they consider the limit for export, if everyone was exporting, before it would cause damage to transformers, etc.
It varies, it can be as low as 3kW. Thankfully, in our cause though, it is 6kW. So we cannot export more than 6kW, legitimately.
Well 9-6 is still 3kW, and whilst I have the hot tub heating during the day, normally, a daytime idle power (when hot tub not heating), is a bit more than 1kW.
The result is, on a really sunny day, we could be exporting 2kW too much. Ooops.
Well, not quite, the inverter is set up to limit to the agreed amount, 6kW. It adjusts the panel optimisers to ensure that overall they are not quite as efficient, if we go over 6kW. So on a sunny day I should see a flat top on my export stats at 6kW. It means I will be literally throwing away some sunshine, up until I get my battery.
Paperwork
However, there is another snag - the final handover paperwork is normally done when the install is complete. The permission covers the solar and the battery - but we have no battery for 4 months - so I have no paperwork. So I cannot get on an export tariff.
The installers are trying to work out with Western Power Distribution how the handle an interim paperwork handover for the solar only without losing the permission to install the battery later. Hopefully something we have sorted shortly.
Tariffs
So the next step is a tariff for the next 4 months. It looks like I can get 5p/kWh from so.energy, less from Octopus unless I move to them for import as well. Octopus also do an agile tariff, but not being able to control when I export (yet, no battery), just relying on sunshine, I am not convinced that makes sense (a variable tariff for every half hour noticed a day in advance).
So my plan for now is probably the 5p/kWh from so.energy for 4 months, if I can confirm how the 12 month minimum works penalty wise. Once I have a battery I will need to revisit tariffs as there are interesting options.
